14 
SEXUAL SELECTION. 
Part II. 
“ orange-coloured stripes, which give it the appearance 
“ of a Labrus, and the body partakes of a golden-orange 
“ tinge. The females are dark in colour, and are com- 
“ monly called black-fish .*’ 20 An analogous and even 
greater change takes place with the Salmo eriox or bull- 
trout ; the males of the char (S. umbla ) are likewise at 
this season rather brighter in colour than the females . 21 
The colours of the pike (Esox reticulatus) of the United 
States, especially of the male, become, during the 
breeding-season, exceedingly intense, brilliant, and iri- 
descent . 22 Another striking instance out of many is 
afforded by the male stickleback (Gasterosteus leiurus), 
which is described by Mr. Warington , 23 as being then 
“ beautiful beyond description.” The back and eyes of 
the female are simply brown, and the belly white. The 
eyes of the male, on the other hand, are “of the most 
“ splendid green, having a metallic lustre like the 
“ green feathers of some humming-birds. The throat 
“ and belly are of a bright crimson, the back of an 
“ ashy-green, and the whole fish appears as though it 
“ were somewhat translucent and glowed with an in- 
“ ternal incandescence.” After the breeding-season 
these colours all change, the throat and belly become 
of a paler red, the back more green, and the glowing 
tints subside. 
That with fishes there exists some close relation 
between their colours and their sexual functions we can 
clearly see : — firstly, from the adult males of certain 
species being differently coloured from the females, and 
often much more brilliantly ; — secondly, from these same 
a> Yarrell, ‘British Fishes,’ vol. ii. lS3ti, p. 10, 12, K5. 
W. Thompson, in ‘ Annals and Mag. of Nat. History,’ vol. vi. 1841, 
p. 440. 
32 ‘ The American Agriculturist,’ 1S68, p. 100. 
23 ‘ Annals and Mag. of Nat. Hist.’ Oct. 1852. 
